1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device and a substrate processing apparatus, and more particularly, to a method of manufacturing a semiconductor device by forming a silicon nitride film by an atomic layer deposition (ALD) method, and a substrate processing apparatus.
2. Description of the Related Art
As one of semiconductor device manufacturing processes, there is a film forming process in which a predetermined thin film is deposited on a substrate by a chemical vapor deposition (CVD) method or an ALD method. In a CVD method, a thin film including elements of source molecules is deposited on a substrate by gaseous reaction and surface reaction of gaseous sources. Among CVD methods, a method of controlling deposition of a thin film on an atomic layer basis is called “ALD method” or “cyclic CVD.” The ALD method is distinguishably characterized in that two or more kinds of source gases are alternately supplied to a substrate to form a thin film, and the thickness of the thin film is controlled by adjusting the repetition number (cycle number) of the alternate supply of the source gases.
In a conventional art, amorphous silicon nitride films are formed in suing a vertical semiconductor manufacturing apparatus (substrate processing apparatus) configured to accommodate substrates (wafers) vertically in multiple stages by an ALD or cyclic CVD method using SiH2Cl2 (dichlorosilane, DCS) and NH3 (ammonia) (for example, refer to Patent Document 1).
A silicon nitride film may be formed on a substrate, for example, by repeating a DCS supply process, a N2 purge process, a NH3 supply process, and a N2 purge process (hereinafter, simply referred to as a cycle treatment). By this, the silicon nitride film can be deposited on the substrate to a predetermined thickness.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-218106
However, a silicon nitride film formed on a substrate by repeating the cycle treatment may have the following disadvantages.
First, due to insufficient nitriding, the silicon nitride film may have poor insulating properties.
Secondly, byproducts may permeate the silicon nitride film to result in poor insulating properties and generation of particles.
Such disadvantages of the conventional art relating to film quality are caused by poor nitriding in a NH3 supply process and are more notable if the process time of a cycle treatment is decreased, the temperature of a substrate is decreased, a silicon nitride film pattern formed on the substrate is fine, or the number of substrates to be batch-processed is increased.
In the conventional art, to solve such disadvantages, the flow rate of NH3 and the time of NH3 treatment are increased while keeping the inside pressure of a process chamber (reaction chamber) constant in a NH3 supply process so as to increase nitriding power. Although the velocity of gas (the flow rate of gas) on a substrate can be increased by the conventional method, since chemical reaction or adsorption reaction are determined by the stay time or concentration of a source supplied to a substrate or the pressure of the source, the conventional method is not so advantageous but the efficiency of gas consumption is decreased and productivity is not improved.